Small
for pets 1-9.9 kg, 81mm H x 75mm W x 120mm L

Medium
for pets 10-24.9 kg, 106mm H x 90mm W x 157mm L

Large
for pets 25-39.9 kg, 106mm H x 100mm W x 205mm L

Extra Large
for pets 40+ kg, 106mm H x 135mm W x 205mm L